Investments in and Advances to Joint Ventures - Service Fees and Income Earned by Company's Unconsolidated Joint Ventures (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Equity Method Investments And Joint Ventures [Abstract]
Management and other fees	$ 5.9	$ 7.4	$ 18.2	$ 22.6
Development fees and leasing commissions	1.4	2.7	4.9	7.9
Interest income	$ 1.7	$ 5.3	$ 5.0	$ 14.4